The invention relates to a plate heat exchanger with a plurality of separating walls stacked one above the other, which alternatingly define a first and second flow space for a first and second medium, a turbulence generator preferably made of sheet metal being positioned in at least one flow space, which generator comprises a plate with a number of parallel-running band-like rows of alternating elevations and depressions mutually connected by bridges, where the elevations and depressions of one row are shifted with respect to the immediately adjacent row, and where each row is provided with at least one transition area for the medium to pass to the immediately adjacent row, such that the depressions of each row are flow-connected with the immediately adjacent elevations of at least one immediately adjacent row.
Plate heat exchangers, especially oil/water heat exchangers consist of a plurality of plates stacked one above the other, forming alternating layers through which a first and second medium flow, for example oil and water. The upwardly bent rim of the plates encloses each layer of the heat exchanger and extends to the rim of the next plate, thus permitting a tight seal against the outside to be achieved by brazing. Inflow of the media occurs through openings in the corner areas of the predominantly rectangular plates.
It is known in the art to furnish the individual units of heat exchangers with internal turbulence generating features, i.e., turbulence generators, to improve heat exchange character-istics of the heat exchanger. In general these turbulence generators induce turbulent flow in the medium flowing through the heat exchanger, thus improving the heat exchange characteristics of the heat exchanger.
In a known type of oil/water heat exchanger turbulence sheets are disposed between individual plate layers, which are brazed to the respective upper and lower faces of adjacent plates during the manufacturing process. These turbulence sheets achieve the following essential objectives:                enlarging the surface for better heat transfer;        generating swirl in the flowing media for better heat transfer;        extending the flow path;        supporting the thin plates against applied pressure;        supporting the thin plates against deformation during the braze-welding process.        
The turbulence sheets are thus core elements of the heat exchanger and largely determine heat transfer performance, flow resistance of both media and mechanical pressure resistance. In the design of an oil/water heat exchanger the following objectives must be met:                maximum heat transfer performance from the oil system to the coolant;        small pressure difference on the oil side;        small or suitably adapted pressure difference on the coolant side;        small dimensions;        a minimum of material required;        simple structure;        good pressure resistance under increasing pressure.        
The principal objective of high heat transfer performance in practice runs counter to almost all other objectives. A narrow structure of the turbulence sheets, for instance, will achieve high swirl and thus good heat transfer, but will also entail high pressure difference. Heat transfer performance will also increase with the space used (number and size of plates), but the latter is to be kept at a minimum for cost and volume reasons. An essential aspect of the turbulence sheets is also their manufacture. Perforated aluminum sheets are usually used, which are formed by a rolling or die-cutting process.